It is intended that a study of the polarized single-crystal spectra of biologically-significant compounds will be continued. Effort will focus on selected purine and pyrimidine bases and their hydrogen-bonded mixed dimers. Work will also be carried out on selected flavins and directed toward completing the study of a series of studies of planar d8 transition metal complexes of biological interest. The major research tool used in this work is polarized reflection spectroscopy, but this approach is augmented by more conventional spectroscopic techniques as is appropriate.